1. Field of the Invention
This invention relates to a diamond sintered body, a process for the production of the same and a tool for cutting or excavating using the diamond sintered body. The diamond sintered body of the present invention is preferably applied to tool materials for cutting or polishing of non-ferrous metals or ceramics, edge materials of drill bits for excavating petroleum or abrasive grains obtained through pulverizing.
2. Description of the Prior Art
Synthetic diamond sintered bodies or materials of the prior art can be classified in three types, depending on sintering materials used:
1 obtained by the use of iron group metals (Fe, Ni, Co) and/or alloys thereof each having a solvent effect, as a sintering binder, PA1 2 obtained by the use of silicon carbide (SiC) as a sintering binder and PA1 3 obtained by the use of a carbonate having a catalytic action as a sintering binder (Japanese Patent Laid-Open Publication Nos. 74766/1992 and 114966/1992). PA1 (a) In the case of the sintered bodies 1 obtained by the use of iron group metals and/or alloys thereof, the diamond is reacted with the binder material to lower the strength when the temperature is raised to 700.degree. C. or higher and the wear resistance or strength is lowered because of use of the metal as a sintering binder. PA1 (b) In the case of the sintered bodies 2 obtained by the use of silicon carbide as a sintering binder, the breakage resistance is inferior because of use of the breakable carbide as a binder material and binding of diamond grains with each other is decreased so that the wear reistance is inferior because of use of silicon carbide free from the solvent action and catalytic action for diamond. PA1 (c) In the case of the sintered bodies 3 obtained by the use of a carbonate as a sintering binder material, the pressure and temperature at which the carbonate exhibits catalytic action are high and the sinterable volume is more decreased as compared with the above described sintered bodies 1 and 2, the cost of the sintered body per unit volume is very high because of a higher sintering cost at an ultrahigh pressure, and the binding strength of diamond grains with each other is so weak that the breakage resistance is inferior, because the carbonate has a relatively small catalytic action and solvent action. PA1 (d) In the case of immersing the above described sintered body 1 in an acid to remove the iron group metals or their alloys, the strength and breakage resistance are both low and use thereof is limited to that at a high temperature. PA1 (1) A diamond sintered body comprising 50 to 99.9 volume %, preferably 50 to 99.5 volume %, more preferably 70 to 99 volume % of diamond and the balance of a binder phase consisting of a single or mixed phase of a compound (C) or composite (C') of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group, Mn, V, alkali metals and alkaline earth metals with a phosphorus compound (B), or of the above described compound (C) or composite (C') with an oxide of (A). PA1 (2) A diamond sintered body comprising 50 to 99.9 volume %, preferably 50 to 99.5 volume %, more preferably 70 to 99 volume % of diamond and the balance of a binder phase predominantly consisting of a material obtained from a rare earth element and a phosphorus compound. PA1 (3) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises mixing a powder of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group metals, Mn, V, alkali metals and alkaline earth metals, a powder of at least one oxide of the element (A) or at least one compound (D) containing the element (A), a powder of phosphorus or at least one phosphorus compound (B) and a powder of diamond or graphite, maintaining and sintering the resulting mixed powders under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (4) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises previously synthesizing a compound (C) of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group metals, Mn, V, alkali metals and alkaline earth metals with at least one phosphorus compound (B) or a composite of the compound (C) and at least one oxide of the element (A), mixing a powder of the compound (C) or composite with a powder of diamond or graphite, maintaining and sintering the resulting mixed powders under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (5) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises previously preparing a thin piece, thin sheet or sintered body holding plate consisting of the compound (C) of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group metals, Mn, V, alkali metals and alkaline earth metals with at least one phosphorus compound (B) or a composite of the compound (C) and at least one oxide of the element (A), combining a powder of diamond or graphite with the thin piece, thin sheet or sintered body holding plate and subjecting the resulting assembly to infiltration under pressure and temperature conditions in the thermodynamically stable region of diamond, thereby sintering the diamond. PA1 (6) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises mixing a rare earth element powder or an alloy powder containing at least one rare earth element, a phosphorus compound and diamond powder or a non-diamond carbon powder or a mixture of diamond and non-diamond carbon powders and maintaining and sintering the resulting mixed raw materials under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (7) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises previously synthesizing a compound from a rare earth element and phosphorus compound, mixing a powder of the resulting compound with diamond powder or a non-diamond carbon powder or a mixture of diamond and non-diamond carbon powders and maintaining and sintering the resulting mixed raw materials under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (8) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises laminating a shaped body of a rare earth element powder or an alloy powder containing at least one rare earth element and a phosphorus compound powder and a shaped body of diamond powder or a non-diamond carbon powder or a mixture of diamond and non-diamond carbon powders and maintaining and sintering the resulting laminate under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (9) A process for the production of the diamond sintered body, as described in the above described (1) or (2), which comprises previously synthesizing a compound from a rare earth element and phosphorus compound, laminating a shaped body of the resulting compound powder and a shaped body of diamond powder or a non-diamond carbon powder or a mixture of diamond and non-diamond carbon powders and maintaining and sintering the resulting laminate under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (10) The diamond sintered body, as described in the above described (1), wherein the phosphorus compound (B) is represented by P.sub.a O.sub.b in which a is 1 or 2 and b is 2, 3, 4, 5 or 7. PA1 (11) The diamond sintered body, as described in the above described (1), wherein the compound (C) or composite (C') is represented by MN.sub.x (P.sub.a O.sub.b).sub.y (OH).sub.z in which M is a simple substance or solid solution of at least one element selected from the group consisting of rare earth elements, alkaline earth elements and 4B elements of Periodic Table and N is a simple substance or solid solution of at least one element selected from the group consisting of Group 3B elements of Periodic Table and sulfur, and x, y and z are respectively in the range of 1.ltoreq.x.ltoreq.4.5, 1.ltoreq.y.ltoreq.5 and 1.ltoreq.z.ltoreq.26. PA1 (12) The diamond sintered body, as described in the above described (1), (2), (10) or (11), wherein the binder phase is composed of a compound (C) or composite (C') of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group metals, Mn, V, alkali metals and alkaline earth metals with a phosphorus compound (B) represented by P.sub.a O.sub.b in which a is 1 or 2 and b is 2, 3, 4, 5 or 7 and an oxide of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group metals, Mn, V, alkali metals and alkaline earth metals. PA1 (13) The diamond sintered body, as described in the above described (1), (2), (10) or (11), wherein the binder phase is composed of a compound (C) or composite (C') represented by MN.sub.x (P.sub.a O.sub.b).sub.y (OH).sub.z in which M is a simple substance or solid solution of at least one element selected from the group consisting of rare earth elements, alkaline earth elements and 4B elements of Periodic Table and N is a simple substance or solid solution of at least one element selected from the group consisting of Group 3B elements of Periodic Table and sulfur, and x, y and z are respectively in the range of 1.ltoreq.x.ltoreq.4.5, 1.ltoreq.y.ltoreq.5 and 1.ltoreq.z.ltoreq.26, with an oxide of at least one element (A) selected from the group consisting of rare earth elements, Group 3A, 3B, 4A, 4B and 6B elements of Periodic Table, iron group metals, Mn, V, alkali metals and alkaline earth metals. PA1 (14) A diamond sintered body comprising 50 to 99.9 volume %, preferably 50 to 99.5 volume %, more preferably 70 to 99 volume % of diamond and the balance of a binder phase predominantly consisting of a material obtained from a phosphorus compound and carbonate compound. PA1 (15) The diamond sintered body, as described in the above described (14), wherein the binder phase is composed of a mixed phase consisting of a material obtained from a phosphorus compound and carbonate compound, and an oxide. PA1 (16) The diamond sintered body, as described in the above described (14) or (15), wherein the binder phase is composed of a mixed phase consisting of a phosphorus-carbonate compound or phosphorus oxide-carbonate compound, obtained from a phosphorus compound and carbonate compound, and an oxide. PA1 (17) The diamond sintered body, as described in any one of the above described (14) to (16), wherein the phosphorus compound contains at least one of rare earth elements, alkali metals, alkaline earth metals, Group 3B, 4B and 6B elements of Periodic Table. PA1 (18) The diamond sintered body, as described in any one of the above described (14) to (16), wherein the carbonate compound contains at least one of rare earth elements, alkali metals, alkaline earth metals, Mn and V. PA1 (19) The diamond sintered body, as described in any one of the above described (14) or (15), wherein the material obtained from the phosphorus compound and carbonate compound contain at least one of rare earth elements, alkali metals, alkaline earth metals, Group 3B, 4B and 6B elements of Periodic Table. PA1 (20) The diamond sintered body, as described in any one of the above described (15) or (16), wherein the oxide contains at least one of rare earth elements, alkali metals, alkaline earth metals, Group 3B, 4B, 6B and 4A elements of Periodic Table, iron group metals, Mn and V. PA1 (21) The diamond sintered body, as described in any one of the above described (14), (15), (16) or (19), wherein the material obtained from the phosphorus compound and carbonate compound is an apatite represented by M.sub.x N.sub.y CO.sub.3 (P.sub.a O.sub.b).sub.z ! in which M is a single element or solid solution of at least one element selected from the group consisting of rare earth elements, alkali elements, alkaline earth elements, Pb, Mn and V, and N is at least one element or oxide, selected from the group consisting of rare earth elements, Group 3B, 4B and 6B elements of Periodic Table and oxides of Group 4A elements of Periodic Table or oxides of metallic elements, and x, y and z are respectively in the range of 1.ltoreq.x.ltoreq.7, 1.ltoreq.y.ltoreq.6, and 1.ltoreq.z.ltoreq.6, a is 1 or 2 and b is 2, 3, 4, 5 or 7. PA1 (22) A process for the production of the diamond sintered body, as described in any one of the above described (14) to (21), which comprises mixing at least one member selected from the group consisting of phosphorus compound powders, carbonate compound powders, phosphorus-carbonate compound powders and phosphorus oxide-carbonate compound powders, at least one oxide powder and diamond powder, and sintering the resulting mixed powders, as a raw material powder, under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (23) A process for the production of the diamond sintered body, as described in any one of the above described (14) to (21), which comprises previously preparing a compound or mixture consisting of at least one member selected from the group consisting of phosphorus compounds, carbonate compounds, phosphorus-carbonate compounds and phosphorus oxide-carbonate compounds and at least one oxide powder, converting it into a powder, mixing the resulting powder and diamond powder, and sintering the resulting mixed powders, as a raw material powder, under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (24) A process for the production of the diamond sintered body, as described in any one of the above described (14) to (21), which comprises mixing at least one member selected from the group consisting of phosphorus compound powders, carbonate compound powders, phosphorus-carbonate compound powders and phosphorus oxide-carbonate compound powders and at least one oxide powder to prepare mixed powders, or previously preparing a compound or mixture consisting of at least one member selected from the group consisting of phosphorus compounds, carbonate compounds, phosphorus-carbonate compounds and phosphorus oxide-carbonate compounds and at least one oxide, converting it into a powder, preparing a thin piece, thin sheet or sintered body holding plate from the mixed powders or the powder, and combining a powder of diamond or graphite with the thin piece, thin sheet or sintered body holding plate and subjecting the resulting assembly to infiltration under pressure and temperature conditions in the thermodynamically stable region of diamond, thereby sintering the diamond. (25) A diamond sintered body comprising 0.1 to 30 volume % of a material consisting of a compound containing Group 3 element of Periodic Table and phosphorus and the balance of diamond. PA1 (26) The diamond sintered body, as described in the above described (25), wherein the compound containing Group 3 element of Periodic Table and phosphorus is a compound consisting of an oxide of Group 3 element of Periodic Table and phosphorus oxide. PA1 (27) The diamond sintered body, as described in the above described (25), wherein the compound containing Group 3 element of Periodic Table and phosphorus is a phosphate of Group 3 element of Periodic Table. PA1 (28) The diamond sintered body, as described in any one of the above described (25) to (27), wherein Group 3 elements of Periodic Table are B, Al and Y. PA1 (29) A process for the production of the diamond sintered body, as described in any one of the above described (25) to (28), which comprises using a phosphate of Group 3 of Periodic Table in the form of a powder, as a sintering agent, mixing a powder of the phosphate with diamond powder or a non-diamond carbon powder or a mixture of diamond and non-diamond carbon powders and maintaining and sintering the resulting mixed powders under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (30) A process for the production of the diamond sintered body, as described in any one of the above described (25) to (28), which comprises laminating a shaped body of a powder of a phosphate of Group 3 element of Periodic Table, used as a sintering agent, and a shaped body of diamond powder or a non-diamond carbon powder or a mixture of diamond and non-diamond carbon powders and maintaining and sintering the resulting laminate under pressure and temperature conditions in the thermodynamically stable region of diamond. PA1 (31) The process for the production of the diamond sintered body, as described in the above described (29) or (30), wherein the phosphate is a phosphate hydrate, hydrogenphosphate or hydrogenphosphate hydrate. PA1 (32) The process for the production of the diamond sintered body, as described in the above described (29) or (30), wherein a mixture of an oxide of Group 3 element of Periodic Table and phosphorus oxide is used as a sintering agent. PA1 (33) The process for the production of the diamond sintered body, as described in the above described (29) or (30), wherein a mixture of an oxide of Group 3 element of Periodic Table and a phosphate of Group 3 element of Periodic Table is used as a sintering agent. PA1 (34) The process for the production of the diamond sintered body, as described in any one of the above described (29) to (33), wherein Group 3 element is boron, aluminum or yttrium. PA1 (35) A diamond sintered body tool for cutting, polishing and excavating, characterized by the use of the diamond sintered body as described in the foregoing items or the diamond sintered body obtained by the process as described in the foregoing items as an edge. PA1 (36) Abrasive grains obtained by pulverizing the diamond sintered body as described in the foregoing items or the diamond sintered body obtained by the process as described in the foregoing items. PA1 a=1 or 2 and b=2, 3, 4, 5 or 7
Type 3 needs sintering at a higher temperature and pressure as compared with Types 1 and 2, resulting in a considerably higher production cost and accordingly, almost all commercially available ones are Types 1 and 2 using the ferrous metals or alloys thereof, and silicon carbide.
In addition to the above described, there are natural diamond sintered bodies (carbonade), which are not actually used on a commercial scale because the origins thereof are not clear, dispersion of the quality is large and the outputs thereof are very small.
The above described synthetic diamond sintered bodies of the prior art have the following problems:
As described above, the diamond sintered body of the prior art meets with at least two problems of i) inferior heat resistance, ii) inferior breakage resistance, iii) inferior wear resistance and iv) needing a high temperature and high pressure by sintering to result in a higher cost.
A diamond sintered body using an iron group metal such as Co, functioning as a catalyst capable of accelerating graphitization of diamond, has inferior heat resistance. Namely, the diamond is graphitized at about 700.degree. C. in an inert gas atmosphere. Moreover, this sintered body does not have such a high strength and tends to be broken because of the presence of the metal such as Co in the grain boundary of diamond grains, as a continuous phase, and there arises a problem that thermal deterioration tends to occur due to difference in thermal expansion between the metal and diamond.
In order to raise the heat resistance, it has been proposed to remove the metal in the above described grain boundary by an acid treatment. Thus, the heat resistance temperature is improved to about 1200.degree. C., but the strength is largely lowered by about 30% because the sintered body becomes porous.
A diamond sintered body using SiC as a binder material is excellent in heat resistance, but exhibits a low strength because of the absence of binding of the diamond grains with each other.
On the other hand, a diamond sintered body using a carbonate as a sintering aid is excellent in heat resistance and has a relatively high strength, but for the production thereof, severe pressure and temperature conditions, for example, at least 7.7 GPa and 2000.degree. C. are required, so that it is difficult to produce it on a commercial scale and it has not been put to practical use. Since carbonates have a lower catalytic capacity and less solubilizing and depositing action of diamond, as compared with the iron group metals of the prior art, furthermore, binding of diamond grains with each other is insufficient, resulting in inferior breakage resistance.